Caption: EDTA and magnesium. Computer graphic of a molecule of the chelating agent ethyldiaminetetraacetic acid (EDTA, C10.H12.N2.O8) surrounding a magnesium ion (Mg, green sphere). The atoms (tubes) of the molecule are colour-coded: carbon (light blue), nitrogen (dark blue), hydrogen (white) and oxygen (red). As a chelating agent, EDTA can bind with positive metal ions (cations) using the nitrogen and oxygen regions of its molecule to form up to six bonds. EDTA is used to preserve DNA (deoxyribonucleic acid) samples by removing the magnesium ions that aid the degradation of DNA. It is also used to detoxify patients suffering from heavy metal poisoning (chelation therapy).